1. Technical Field
The present invention relates to the maintenance of a data processing system. More particularly the present invention relates to a method for determining the topology (or structure) of a storage subsystem of a data processing system, monitoring the status of the subsystem and automatically responding to perturbations in the subsystem.
2. Description of the Related Art
The management of storage devices and sets of data on large data processing systems and mainframe computers is a known problem. Most large computer systems have a hierarchy of storage devices ranging from magnetic tape cartridge data storage devices which have slow access time to direct access storage devices (DASD), which have a relatively fast access time. Typically, the hardware configuration of computer systems is constantly undergoing change i.e. new DASDs may be introduced and others removed or replaced. In the case of interconnected systems, arrangements as to whether particular DASDs are shared between processors may also be subject to change. Also, restrictions may be imposed to limit the sharing of DASDs subject to certain conditions being met. DASDs may be shared between processors to save disk space or when they are being used to store a program library.
An example of an interconnected data processing system is shown in FIG. 1. The central computer system 10A is connected to remote target computer systems 10B and 10C. The computer systems 10A, 10B and 10C have associated direct access storage device (DASD) storage, i.e. DASDs 30A, 30B and 30C are associated with the processor of 10A via I/O controller 40A. DASDs 30D, 30E, 30F and 30C are associated with the processor of 10B via I/O controller 40B. DASD 30C is shared between processor 10A and 10C. In such a system both 10A and 10B may be aware that DASD 30C is shareable but, neither processor can determine the identity of the other processor.
Each DASD has a unique serial number or physical identifier associated with it. This physical identifier is not actually utilized by the processor but is used by service engineers as an address for locating the physical position of a DASD for the purpose of replacing it or performing maintenance on it. The processor communicates with storage space on a DASD by means of a logical address. The actual physical positions and physical connections of DASDs are not known by the processor.
As data processing systems are expanded and modified there is a problem in recording and keeping track of the physical configuration of the direct access storage devices and their control units, especially in the case of interconnected processor complexes. Prior art methods of keeping track of DASDs tend to be quite primitive and involve a great deal of human interaction and manual typing of data.